Process for manufacturing shapes from homogeneous alloys of great hardness



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EDUARD SCHNEBEL, OF TBAUNSTEIN, GERMANY, ASSIGNOR TO FRIED. KR'UPB ,AK'IIEN- GESELLSCEAFT, OF ESSEN-ON-THE-RUHR, GERMANY v PROCESS FOR MANUFACTURING SHAPES, FROM HOMOGENEOUS ALLOYS OF GREAT HABDNESS No Drawing. .lpplication filed July 19, 1929, Serial No. 379,565, and in Germany July 17, 1925.

The subject-matter of the invention is a new process for manufacturing shapes such as tools or tool parts, of homogeneous alloys of reat hardness.

rocesses are already known the object of which is to produce bodies of high mechanical resistance and of such a hardness that they can be used in place of diamond tools. In practical use certain carbides, silicides and borides of metals having a high melting point primarily are employed for this purpose.

.Serious difiicultiesare encountered however in technically treating these materials. If tools are to be manufactured thereof by casting, comparatively high temperatures are required to fuse them. Besides, these materials have the far more serious drawback that their melt freezes with comparatively large crystals that cohere only slightly, so that bodies produced in this manner possess only a very low resistibility, if any to mechanical stresses. This disadvantageous property is increased by the strong tendency of the melt of these 'materials, to segregate heterogeneous constituents in freezing.

An attempt was made to overcome these difficulties by adding to the pulverized carbides, silicides, or borides of metals metallic binding means, such as iron, cobalt or nickel, and producing by a pressing operation shaped bodies of these mixtures which bodies then were subjectedto a sintering process.

In this manner, .to be-sure, shapes can be produced at much lower temperatures than required in the casting process. This method, however. hasthe serious disadvantage that the hardness of the starting material is'considerably reduced by the addition of said metals as binding means.

Another way to overcome the difficulties set forth consists in heating the carbides, silicides and borides not beyond their melting point but only up to the vicinity thereof. By this measure, at least in the employment of carbide of tungsten and of molybdenum, it is possible to make tools that possess both the hardness of the starting material and a remarkable mechanical strength.

But even if small quantities of other metals are added in this process to enlarge the range of the most favorable temperatures, which range is below that of complete liquefaction, considerable difficulties are encountered in carrying out this method in practice. If the most favorable conditions of temperature are not observed very accurately, it is inavoidable that a high percentage of the products becomes of inferior value.

By slightly surpassing the most favorable interval of temsions. Finally, it is nearly impossible to pro duce by this process tools which consist of carbon alloys of the metals of high melting temperature, that are not saturated with carbon at the optimum temperature, but never-- theless possess properties of particularly high value for many purposes. The occurrence of big pipes and pores is inavoidable in such tools- The difliculties h'ereinbefore set forth are completely avoided by the process that forms the subject-matter of the invention. This process consists in the following: A homogeneous alloy-is made first, by melting and subsequent heat treatment, which alloy has a .fine texture such as to possess the maximum hardness and maximum resistance to wear with respect to the intended application. This starting material which is homogeneous throughout its smallest particles is finely powdered, and. after having been brought to the shape of the desired tools by applying 'high pressure and suitable pressing tools, is

subjected to a heating process in an indifferent atmosphere. This heating may beiichieved in any desired manner, both external heat supply or resistance heating of the shaped body being applicable. It is further immaterial for the substance of the invention whether the application of pressure and the heating take place successively or simultaneously, Care must be taken in heating not to reach nor exceed thosecritical points of the alloy in consideration where recrystallization starts and the fine texture is altered. Therefore the sintering temperature should in most cases be below about 1900 C. Surprisingly one subceeds in this Way, probably due to the entirely homogeneous composition of the alloys treated, in producing tools which both possess the full hardness of the starting material and are quite free from pipes and pores, and possess a particularly high mechanical. strength.

The properties of the tools thus produced are best when both the melting of the starting material and the heating of the shaped bodies produced by pressing is carried out in the presence of indifferent gases and under a pressure below atmospheric. It is further of great advantage to subject the shaped bodies immediately after the heating to a heat treatment which causes an improvement of the fine texture of the tools. This measure is of particular advantage when a deterioration of the fine texture has been caused during the second stage of the process by exceeding critical points.

The present process can be employed with advantage also for the manufacture of tools the structure of which can be improved by mechanical treatment such as forging, rolling, pressing, etc., in some cases with heating to a higher temperature. Furthermore, holes, recesses and the like can be provided on the tools directly by the pressing operation. I

The additions to be made to the metals of high melting point, more particularly the metalloids, can be added to the mixture only in the course of the melting process, for instancefrom the crucibles. The additional metals can be replaced wholly or pautly by metalloids. Particularly advantageous properties will be ossessed by melts in which the carbon bound by tungsten amounts to less than 3%.

In producing the tools or parts thereof one proceeds for instance in the following manner:

400 gr. powdered tungsten are mixed with 40 gr. carbide of titanium. The mixture is brought into a carbon crucible having carbon terminals and is heated electrically in a hydrogeno'us atmosphere up to melting. The carbon required for the alloy is taken up by the melt both from the carbide of-titaniuin and from the carbon crucible. Immediately after the molten state has been reached, the

molten mixture is cast into a mould. of-copper which is cooled by water whereby a very finely grained texture is obtained which is entirely free from segregationsf The melt is thereupon finely pulverized and'pressed with produced in this manner are subJected to a sintering process by exposing them during about 12 minutes to a temperature of about 1750 degrees in a hydrogen current, cooled down to 1500 degrees within 40 seconds and thereupon further cooled to room temperature within 45 minutes.

What I claim and desire to secure by Letters Patent, is

1. A process for producing shapes of homogeneous alloys of great hardness, consisting in melting amixture of at least one metal of high melting point with at least one metalloid of the carbon group and subjecting the molten mass to a texture refining heat treatment, pulverizing the alloy so formed, pressing the pulverized alloy into shapes, and sintering said shapes at a temperature below the recrystallization temperature of, the alloy.

2. The process for producing shapes of homogeneous alloys of great hardness, consisting in melting a mixture of at least one metal of high melting point with a metalloid of the carbon group and at least one additional metal, subjecting the molten mass to a texture refining heat treatment, pulverizin the alloy so formed, pressing the pulverize alloy into shapes, and sintering said sha at a temperature below the recrystallization temperature of the alloy.

3. The process for producing shapes of homogeneous alloys of great hardness, consisting in melting at least one metal of high melting point, adding during the melting process a metalloid of the carbon group, subjecting the molten mass to a texture refining heat treatment, pulverizing the alloy so formed, pressing the pulverized alloy into shapes, and sintering said shapes at a temperature below the recrystallization temperature of the alloy.

,4. The process for producing shapes of homogeneous alloys of great hardness, consisting in melting a mixture of at least one metal of high melting point with severalmetalloids of the carbon group, subjecting I the molten mass to' a texture refining heat treatment, pulverizing the alloy so formed, pressing the pulverized alloy into shapes, and

sintering said shapes at a temperature below subjecting the molten mass to a texture refining heat treatment, pulverizing the alloy so formed, pressing the pulverized alloy into shapes, and 'sintering said shapes at a hametaaea perature below the recrystallization temperature of the alloy.

6. The process which consists in melting an alloy of tungsten, carbon, and at least one additional metal, in which alloy the proportion of carbon boundto the tungsten is less than 3%, subjecting the molten massto a texture refining heat treatment, pulverizin the alloy so formed, pressing the pulverize alloy into shapes, and sintering said shapes at a temperature below. the recrystallization temperature of the alloy.

7. The process as specified in claim 1, in

which said melting and sintering operations are executed in an indifferent atmosphere and under reduced-pressure.

8. The process as specified in claim 1, in combination with the step of subjecting the shapes after the sintering operationto a heat treatment adapted to improve their propertiesand consisting in cooling-down quickly from the sintering temperature to about 1300-1600 degrees, C. and thereupon further cooling slowly to room temperatur 9. The process as specified in claim 1 in which any desired holes or recesses are formed in the shapes during the ressing operation. The foregoing spec' cation signed at Munich, Bavaria, Germany, this 21st day of June, 1929.

EDUARD SOHNEBEL. 

